Troglitazone reverses the multiple drug resistance phenotype in cancer cells

Abstract

A major problem in treating cancer is the development of drug resistance. We previously demonstrated doxorubicin (DOX) resistance in K562 human leukemia cells that was associated with upregulation of glyoxalase 1 (GLO-1) and histone H3 expression. The thiazolidinedione troglitazone (TRG) downregulated GLO-1 expression and further upregulated histone H3 expression and post-translational modifi cations in these cells, leading to a regained sensitivity to DOX. Given the pleiotropic effects of epigenetic changes in cancer development, we hypothesized that TRG may downregulate the multiple drug resistance (MDR) phenotype in a variety of cancer cells. To test this, MCF7 human breast cancer cells and K562 cells were cultured in the presence of low-dose DOX to establish DOX-resistant cell lines (K562/DOX and MCF7/DOX). The MDR phenotype was confi rmed by Western blot analysis of the 170 kDa P-glycoprotein (Pgp) drug effl ux pump multiple drug resistance protein 1 (MDR-1), and the breast cancer resistance protein (BCRP). TRG markedly decreased expression of both MDR-1 and BCRP in these cells, resulting in sensitivity to DOX. Silencing of MDR-1 expression also sensitized MCF7/DOX cells to DOX. Use of the specifi c and irreversible peroxisome proliferator-activated receptor gamma (PPARγ) inhibitor GW9662 in the nanomolar range not only demonstrated that the action of TRG on MCF/DOX was PPARγ-independent, but indicated that PPARγ may play a role in the MDR phenotype, which is antagonized by TRG. We conclude that TRG is potentially a useful adjunct therapy in chemoresistant cancers.

Activation of the Anaphase Promoting Complex Restores Impaired Mitotic Progression and Chemosensitivity in Multiple Drug Resistant Human Breast Cancer

“…Next, we assessed MDR and APC substrate protein levels in DOX selected MCF7 cells to ensure that it was not a drug-specific effect, as TAM and DOX are unrelated first line therapeutics for breast cancer. As anticipated, higher levels of MDR protein markers (TFPI) were observed (Figure 2C), as shown previously [27,32,38]. Furthermore, higher APC substrate protein levels (CDC20 and Cyclin B1) were present.…”

“…The reciprocal co-immunoprecipitation experiment was performed (Figure 1F) with consistent results, again showing decreased CDC27 associations with CDC20 specifically in resistant cells. Furthermore, we used antibodies against protein markers of MDR (BCRP, MDR-1 and TFPI) [9,27,32,38] and DNA damage (gH2AX) [39] to confirm that the TAM selected cells are indeed multiple drug resistant and experiencing higher levels of DNA damage (Figure 2A,B; two separate experiments done independently are shown in A and B). Our data shown here indicates that the reduction of CDC20 and CDH1 interactions with CDC27 are not cell cycle specific and reflect an impairment of both APC CDC20 and APC CDH1 .…”

Activation of the Anaphase Promoting Complex Reverses Multiple Drug Resistant Cancer in a Canine Model of Multiple Drug Resistant Lymphoma

“…To identify the underlying cellular pathways involved in MDR development, and to identify novel agents that will promote reversal or prevention of MDR cancers, we previously applied in vitro MDR cell culture models of a variety of human cancers to identify molecular biomarkers and their post-translational modifications that correlate with both entry to, and exit from, an MDR state [ 6 , 7 , 8 , 9 , 10 ]. Simultaneously, we evaluated the utility of several insulin-sensitizing oral agents with anti-cancer activity that returns MDR cells to treatment-sensitive states [ 7 , 8 , 10 ]. Metformin, a drug used to treat type 2 diabetes globally, as well as a number of other diseases [ 11 ], can slow the growth of multiple human cancer cells in vitro [ 12 ].…”

Activation of the Anaphase Promoting Complex Restores Impaired Mitotic Progression and Chemosensitivity in Multiple Drug Resistant Human Breast Cancer

“…The reciprocal co-immunoprecipitation experiment was performed (Figure 1F) with consistent results, again showing decreased CDC27 associations with CDC20 specifically in resistant cells. Furthermore, we used antibodies against protein markers of MDR (BCRP, MDR-1 and TFPI) [9,27,32,38] and DNA damage (gH2AX) [39] to confirm that the TAM selected cells are indeed multiple drug resistant and experiencing higher levels of DNA damage (Figures 2A, 2B; two separate experiments done independently are shown in A and B). Our data shown here indicates that the reduction of CDC20 and CDH1 interactions with CDC27 are not cell cycle specific and reflect an impairment of both APC CDC20 and APC CDH1 .…”